How to save data in Core Data? - objective-c

Question

I created an entity named House. This entity has two attributes which are street (of type string) and numOfStories (of type integer 32). I was able to successfully save and NSLog data in my AppDelegate.m didFinishLaunchingWithOptions method. However, when I try to make 2 textfields and show the User's input, and make a button to save, the result is SIGABRT.
Here is all the code I'm using in my MainViewController.m:
- (BOOL)createNewHouseWithStreet:(NSString *)paramStreet numOfStories: (NSUInteger)paramNumOfStories
{
BOOL result = NO;
if ([paramStreet length] == 0)
{
NSLog(#"Street name is mandatory");
return NO;
}
House *newHouse = [NSEntityDescription insertNewObjectForEntityForName:#"House" inManagedObjectContext:self.managedObjectContext];
if (newHouse == nil)
{
NSLog(#"Failed to create the new House");
return NO;
}
newHouse.street = paramStreet;
newHouse.numOfStories = #(paramNumOfStories);
NSError *savingError = nil;
if ([self.managedObjectContext save:&savingError])
{
return YES;
}
else
{
NSLog(#"Failed the save the new House. Error = %#", savingError);
}
return result;
}
and below this I have
- (IBAction)save:(id)sender {
[self createNewHouseWithStreet:#"10 WYOMING" numOfStories:2];
[self createNewHouseWithStreet:#"6 WYOMING" numOfStories:3];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:#"House"];
NSError *requestError = nil;
NSArray *houses = [self.managedObjectContext executeFetchRequest:fetchRequest error:&requestError];
if ([houses count] > 0)
{
NSUInteger counter = 1;
for (House *thisHouse in houses)
{
NSLog(#"House %lu Street Name = %#", (unsigned long)counter, thisHouse.street);
NSLog(#"House %lu number of stories = %ld", (unsigned long)counter, (unsigned long)[thisHouse.numOfStories unsignedIntegerValue]);
counter++;
}
}
else
{
NSLog(#"Could not find any House entities in the context.");
}
}
So what's weird is that this code ends up resulting in sigabrt whenever I tap the save button, but when I put the code from the save method into my AppDelegate.m didFinishLaunchingWithOptions method it works great.
All help is appreciated, thanks.